A gamma ray detector that utilizes the kinematics of Compton scattering is disclosed in JP Patent Publication (Kokai) No. 9-101371 A (1997) or JP Patent Publication (Kokai) No. 2005-208057 A as a gamma ray detector that can detect the position of a gamma-ray source or an arrival direction of gamma rays without using a collimator. The aforementioned gamma ray detector uses two germanium detecting elements that have a position resolution and an energy resolution, and focuses on a gamma ray detection event in which a gamma ray incident on a front germanium detecting element undergoes Compton scattering, and thereafter the scattered gamma rays are incident and absorbed by a rear germanium detecting element to thereby calculate a position or a direction in which a gamma-ray source exists based on the detected positions and detected energy of the gamma ray at the two germanium detecting elements. In “T. Tanaka et al.: ‘Development of a Si/CdTe semiconductor Compton telescope’, Proceedings of SPIE 5501 (2004) pp. 229-240”, an image pickup apparatus for gamma-ray astronomy is described that applies the same principle by combining a silicon detecting element and a cadmium telluride (CdTe) detecting element.
Patent Document 1: JP Patent Publication (Kokai) No. 9-101371 A (1997)
Patent Document 2: JP Patent Publication (Kokai) No. 2005-208057 A
Non-Patent Document 1: Proceedings of SPIE 5501 (2004), pp. 229-240